Thermal drive method for recovery of oil



Feb. 5, 1952 E. s. MERRIAM ETAL 2,584,605

THERMAL DRIVE METHOD FOR RECOVERY OF on.

Filed April 14, 1948 Patented Feb. 5, 1952 UNITED STATE THERMAL DRIVE METHOD FOR RECOVERY OF OIL Edmund S. Merriam, Marietta, Ohio, and

Frederick Squires, Champaign, Ill

Application April 14, 1948, Serial No. 21,004

16 Claims. 1

This invention relates to the recovery of petroleum. More particularly, the invention relates to a method for the recovery of oil from oil sands which are located in geological formations inter- "stratified with coal seams, ligneous deposits or other combustible organic matter.

Petroleum is usually found associated with sandstone or porous limestone deposits situated between impervious layers of shale, or rock and the like. -In most instances, the 011 contains lighter gaseous hydrocarbons, such as methane,

ethane, propane, etc., which may exist as free gases in contact with the oil or dissolved in the "oil itself. The pressure under which the oil and associated gases exist is equal to the hydrostatic pressure of a column of water equal to the depth ofthe deposit below the surface. When such an oil bearing sand is reached by drilling, oil is "produced by flowing to the surface under the expansive force of the gases at well pressures, whether the gases are free or dissolved in the liquid oil. ,Thus, the oil and gas are both forced into-the region of low pressure around the well bottom. Depending upon the total pressure exerted, and the conditions at the mouth of the Pumping is then initiated in order to continue to recover oil. During this stage, gas associated "with the oil continues to escape from the casinghead. Subsequently, the flow of oil becomes economically unprofitable with respect to further utilization of pumping means.

When the well attains this condition in which the heavier hydrocarbons obstruct the pores of the sand and no longer flow freely to the well bottom, the method of repressuring the well system is commonly practiced. This involves forcing back into selected. central wells' air or gas which penetrates the sands and finds exit from the adjacent wells communicating with the oil reservoir under treatment. The air or gas mechanically forces the crude oil to the venting well bottoms where it is removed by pumping, and the more volatile portions of the residual oil are entrained in the gas or air stream and thus removed from the we In time repressuring becomes no longer expedient, and final resort may be had to the flooding of the oil field with water to drive additional amounts of the'residual oil contained in these 2 v sands into the wells. -After flooding has been utilized to the point where it is no longer profitable, the flooded field becomes non-productive and must be abandoned.

It is well known that in thefields subjecte to the foregoing treatment, nearly half of the oil known to be initially present is still left as residual oil in the sands. At the present time, the problem of recovering this-vast amount'of residual oil hasbecome an urgent one, particularly due to the increasing demand for petroleum and petroleum products, and the rapidly diminishing number of discoveries of new oil fields.

It has heretofore been recognized that oil may be recovered by-applying' heat to oil-containing sands in their native position. Bythus heating the oil-containing sands, the heavier hydrocarbons clogging the pores of the sand are rendered less viscous, and the flow thereof through the sand is facilitated. In addition, 'themore volatile hydrocarbons are distilled from the sand to the venting well casing. Various methods have been proposed for effecting a heating of'the oil sands. For example, direct combustion of a portion of the residual oil utilizing air under pressure, orair and acombustible gas to initiate and support combustion of the oil has been proposed.

It has also been proposed to pass heated products of combustion in gaseous form through'the oil sands in order to effect a heating thereof, whereby the viscosity of the residual oil is reduced and the oil becomes more mobile. However, these prior methods have-certain inherent disadvantages which are obviated by the present invention.

Where direct combustion of a portion of the residual oil is practiced, it is extremely difficult to control the extent of combustion, and regardless of control, the method inherently involves destruction of an appreciable portion of the oil itself. On the other handfthe method employing heated products of combustion, necessitates a continuous supply of combustible gases, which supply must be immediately available at the location in order to render the method feasible. In addition, useof gas requires that the gaseous products of combustion be introduced into the oil coal seams, ligneous deposits, or other combustible organic matter represent an available source of potential heat energy far in excess of the amount which would be required to supply a thermal drive by which oil in the adjacent oilcontaining sands may be heated and thereby recovered. The present invention is directed to a method in which ithe. heat .energy existing such coal "seams, ligneous deposits and other combustible organic matter is utilized in situ, thus supplying the heat necessary for recovery of the oil in the oil-containing sands. In addition, the invention contemplates the use ;of;such deposits of combustible organic matter as the source of fuel necessary to provideithe'mechanical energy for operation of the process.

It is, therefore, a primary object and purpose of the present invention to provide a method for the recovery of oil from oil reservoirs located in geological formations interstratified with iother 'combustible organic matter.

it is a"-further "object or the invention *to prowide ea method ior-recovery 'o'f oil in which a thermal drive for effecting-releaseo'f' the'oil from 'the oil-containing sands is created by combus- :tion :ofccombustible organic matter adjacent to the oil sands.

Ibis-another object-of the invention to provide a iainethodfor the recoveryxof oil "from oil-con- 'taining sands andthe 'likein'which no source of E heat'produced above ground 1 is employed.

A'Another object :of theiinvention 'is to utilize the products .ofrcombustionrof the combustible organicvmatterasr'a' source .of fuel for supplying fth'e mechanical energytnecessary for operation zofrthe process.

Titus-a1 still? further object of the "invention to rprovide a :method for the :recovery of oil from oil-containing sands and the like in :which destruction of :the residual :oil :by :combustion is substantially a avoided, .while sufiicient heat is supplied to effect :efiicient recovery of oil.

Aa'further: object :oftheiinvention is to provide armethod-tfor thewrecovery f .oil in :which the "recovery is 'facilitatedtby-xmeans :of heat emanatin'g irom awsubterranean source adjacent to or conta'ined -in the oil-containing sands 'or' the like.

Another object 'of the invention is to provide =a' method for establishing a .channel :through a subterranean seam :of combustible organic matter.

Essentially, 'the TmBthOd' of the present. inven- -tion comprises subjecting coal, ligneous or other combustible organic matter interbanded withthe "oil-containing sandsrto combustion, thereby fur- :nishing :the heat which effects a :distillation of the-more yolatileportionsof :theoil and fluidizes :the remainingxportionstof the oil byrendering it less viscous,.andthen withdrawing the vapor- -ized.:and"fluidized :oil.

with combustion occurring along the entire length 'oifrthe veinzofrzcombustible organic matter, "ai large portion of the adjacent oil sands are effectivelyheated by conduction through the interveningl'layers of shale or-rock and the like. 'This'iincrease in temperature-of the oil-contain- 'i-ng sands renders :more 'fluid the semi-solid hydrocarbons "cloggingzthepores of 'thesand, that is, their viscosities are greatly reduced. Any nor- -mally solidrhydrocarbons which may have previously abeen precipitated are redissolved in the liquefied-hydrocarbons. In all cases the heavier =izyd-rocarbon liquids become less viscous and rmosne mobile. .lnraddition, the vapor pressureof 4 both the connate water and the hydrocarbons of the oil are greatly increased. This causes an increase in the pressure existing in the oil-containing sands. The thus volatilized and fluidized residual oil moves in the direction of a zone of lower pressure which exists at the communicating well bottoms and is there withdrawn by "suitable means :such as.pumping.

In order to provide'for initiating and maintaining combustion of the seam of coal, lignite stratified with respect to the oil-containing sands. This may be accomplished simply by I drilling as in'the case of oil wells, or by sinking a :shaft of .relatively larger diameter as is customarily done for water wells, or by operating from existing coal mines.

In order to actively burn a subterranean seam ofqcoal 'or'the .like,:a combustion supporting :gas :inust continuously 'pass through .such .seam.

Underzthese conditions-after ignition of the :coal or other combustible'zorganic matter at one end -,of the seam, combustioncontinuously progresses along the length of the seam. In general, maintenance of combustion is insuredpnly by establishing a direct path or channel for'the com- :bustion supporting gases through thelength'of the seam. One of theprincipal features 'of the presenttinvention is the'provision of means for "establishing horizontal channels along the length 'of such seams of combustible organic matter. In addition, the invention contemplates locating the end of such path or channel with respect to the surface. and establishing communication therewith from the surface to provide a continuous passage for the combustion supporting gasesand gaseous products of combustion. The combustion supporting, gases may then be .con-

- tinuously passed down'through the input shaft ume of combustion-supportinggas to'pass through the channel with consequent combustion of increasing amounts of the coal or the like.

In some instances, a coal or lignite seam is found to be sulficiently permeable to the combustion supporting gases injected under suitable "pressure to allow ignition at one end thereof and continued combustion without the necessity of .establishing a channel through the seam.

Heat from combustion of the coal or the like passes to the adjacent oil-containing sands by conduction through any intervening shale deposits or the like. The oil being highly heated develops an increased pressure, and the more vol- :atile portion is distilled out of the sands, while the heavier hydrocarbon portions are rendered suiiiciently fluid to be recovered .by draining or forcing toward zone of lower pressure.

Various procedures may be utilized to recover the oil according to the thermal drive method of the invention. Two or more wells may be drilled .at .selected positions within the heated zone. These wells communicate only with the oil sands.

5, Byintroducing a gas under pressure into one of such oil wells, the heated vaporized and fluidized oil is forced into the otherwel1 or wells communicating with the oil sands and is removed therefrom by any suitable means, such as pumping. Of course, existing oil wells adjacent to the seam of burning combustible organic matter may be utilized as the repressuring and producing wells. Also-the gaseous products of combustion issuing from the chimneygor exit well communicating with the seam of burning coal or the like may be used, as the repressuring gas.

Alternatively, if the input shaft and/or the chimney well communicating with the seam of coal or the like also communicate with the oil sands, they maybe employed as the oil producing wells. 1

In the foregoing embodiments of the invention, the wellsemployed as the oil producing wells may be selected so that the how of oil is either concurrent or countercurrent with respect to the flow of heat within the heat zone created by combustion of the seam of coal or the like.

7 According to the above procedures, only that portion of the heat from the combustion which is transmitted both vertically and horizontally by conduction through intervening strata is utilized toeffect a heating of the oil. In other words, the sensible heat contained in the gaseous products of combustion is not utilized to heat the oil sands, c and passes with these products out through the exit or chimneywell.

Since the coal, lignite or other combustible organic matter burned in this manner is'in excess of the oxygen contained in the combustion supporting Such as air, the Should such a problem exist, still another algaseous products of combustion issuing from the chimney well will contain appreciable amounts of carbon monoxide and other combustible gases, together with smoke and tar vapors. They comprise essentially a good type of producer gas. Such products of combustion may be utilized as fuel for boilers or the like in order to operate prime movers which drive the necessary blowers, compressors, etc. These gases may also be utilized as fuel for the refinery and gasoline Plants if the *1 zone oi'heat created by combustion of the seam same are located in the area.

It is a preferred embodiment of the invention, however, to effect a substantially complete utilization of the sensible heat contained in the gaseous products of combustion. This may be accomplished in thefcase where communication exists between the chimney well and the oil-containing sands by closing the chimney well after ignition of the coal seam. The gaseous products of combustion are thus forced from the chimney well through the adjacent oil-containing sands by the pressure of the continuous stream of combustion supporting gas introduced into the input shaft and the channel in the coal seam. In this manner, substantially all of the available heat created by combustion of the seam is realized as heat input to the residual oil in the oil-containing sands. The oil is recovered either from the input shaft which also communicates with the oil sands or from a separate producing well in the zone of heating.

" The volume of the gaseous products of combustion exceeds the volume of combustion supporting gas necessary to maintain active combustion of the coal. With the chimney well closed a high pressure is developed in situ in the channel located in the coal seam and in the chimney well bore and bottom. By increasing the pressure of the combustion supporting gas supplied to the seam to a value in excess of the pressure developed by the products of combustion, the heated gaseous products of combustion are forced into and through the oil-containing sands imparting additional heat thereto. Thus, the sands containing the oil are not only heated by direct conduction through the intervening strata and by the sensible heat contained in the products of combustion, but also a positive drive due to the pressure developed is set up within oil sands. This mechanical drive facilitates movement of the vaporized and fluidized residual oil toward the zone of lower pressure, at the producing well bottom. The total volume of combustion gases may exceed the amount desired for introduction into the oil sands. In such instance the excess gas may be passed to repressuring wells in the system which do not communicate with the burning seam. In the case where the oil sands do not communicate with I the chimney well or input shaft for the coal seam, the hot gaseous products of combustion issuing from the chimney well are forced under pressure into the repressuring well and thus into the oil sands. The sensible heat therein is thus imparted to the oil.

In some instances where the combustion of the coal, ligneous material or other organic com bustible matter is quite incomplete, the products of combustion in gaseous form will contain condensable vapors of tarry. or resinous material. In such case, the condensable tars and the like may precipitate after coming into contact with cooler regions of the oil-containing sands and rapid, clogging of the porous sands may ensue.

ternative embodiment of the present invention may be adopted.

Accordin to this alternative procedure, the chimney well for the burning coal seam is left open to act as an exit for the gaseous products of combustion containing the condensable tarry materials which may be utilized as fuel, as mentioned above. Communication is established with the oil-containing sands only within the of coal or the like. In some instances, this may be accomplished by utilizing existing wells communicating only with the oil sands. In this embodiment there can be no communication between the end of the coal seam entering the chimne well and the oil-containing sands. If such communication exists, it is eliminated by the use of packers or by cementing. Air or other gas under pressure is then supplied to the oilcontaining sands through this repressurin well to provide a positive drive for the heated residual oil through the sands to the producing well or Wells.

In order to advantageously utilize the sensible heat contained in the gaseous products of combustion, while employing this alternative procedure the following refinement of this procedure may be adopted: The pipeline for supplying air or gas to the oil-containing sands is positioned in heat exchange relation to the hot gaseous products of combustion issuing from the chimney well. Thus, heat exchange will occur between the repressuring air or gas and the highly heated gaseous products of combustion, whereby the sensible heat in the products of combustion will be extracted by the air and the heat thus absorbed by the air will be carried into the oilcontaining sands.

A second alternative method to prevent clogging of the oil sands by the condensable tars and resinscontained in the gaseous products of combustion may be adopted. In this alternative embodiment of the invention, communication exists between the oil sands and the chimney well. The chimney well is closed after active combustion of the coal or the like has been initiated. Air under pressure is then introduced through the capped chimney well by a pipe extending to the bottom of the well in order to completely burn the organic material, such as the condens able tarry vapors resulting from the incomplete combustion of the coal or the like. If necessary, a gas burner is introduced into the bottom of the chimney well to aid in completing the combustion of the products resulting from the burning of the coal. Thus, the hot clean gases produced by complete combustion at the bottom of the chimney well, together with the gases produced by the burner operation, penetrate the oil-com taining sands by the pressure developed in situ. and impart the sensible heat contained therein to the sands driving the oil out by distillation and by mechanical movement to the zone of lower pressure at the producing well bottom.

As stated above, some of the naturally occurring coal or lignite seams are sufliciently perrneable to gases to allow ignition thereof and main tenance of combustion by penetration of combustion supporting gases. However, in most instances a direct channel or path must be established in the seam to be subjected to combustion.

The present invention contemplates the use of several means for establishing a path for the combustion supporting gases through the seam of combustible organic matter.

Known methods of horizontal drilling may be employed. These involve operating from a mine, from a shaft, or from a well. For instance, one method is to sink a well to the seam of coal or the like and greatly enlarge the hole at the coal level by shooting. An unbrella type of whipstock can then be lowered to the shot hole and spread into position. A flexible cable carrying a rotating bit is then operated from the whipstock in order to effect horizontal drilling. In this manner, a direct path or channel of the desired length may be produced in the seam of coal or the like to be burned.

The final position of the bit at the end of the horizontal bore with respect to the surface is then determined. This may be done in several ways. For example, the compass method may be employed in which a compass of the marine type having a needle imbedded in parafiine or the like attached to a flexible cable is pushed to various positions along the bore. The paraifine is electrically melted and then allowed to resolidify, thus fixing the position of the magnet at the given point. A plot of the location of the horizontal bore may then be made, and knowing the position of the original well, a second well may be drilled to communicate with the end of the horizontal bore. A second method consists of plotting electrical resistance between an electrode at the end of the bore hole with another electrode moved to various positions on the surface. In this manner, the point on the surface vertically above the end of the horizontal bore may be determined. A well is then drilled to establish communication with the end of the horizontal bore.

The lower end of the drilled well will not in all probability initially directly communicate with the end of the horizontal bore. However, it will be located immediately adjacent to the bore, and

8. communication may be established by exploding charges inserted into the well bottom and into the end of the horizontal bore.

A communication is thereby established between the flrst and second well, or between a mine or shaft and the second well. The second well serves as a chimney or exit well for the gaseous products of combustion at least when the seam is first ignited. Combustion is then maintained by continuously supplying the combustion supporting gas to the seam through the first or input well and the coal actively burning constantly enlarges the horizontal bore through the seam. Irregularities in direction and partial obstruction in the channel within the seam are of little consequence as they will burn away.

Another method by which a direct path or channel may be produced in the seam oi. the coal or the like is effected by hydraulic lifting within the seam. In this method an incompressible fluid, such as oil or water, is forced down an existing or drilled well which is in communication with the seam. The fluid is placed under a pressure greatly in excess of the pressure existing in the seam. For example, a pressure of one pound per square inch for each foot of depth must be exceeded. In an adjacent existing or drilled well communicating with the seam to be channeled, the fluid is also introduced under the same pressure. The fluid under this pressure acts as a hydraulic jack and causes the seam to separate along the lines of weakness. An actual channel is thus formed between the two wells. After a channel is established, the pressure on the fluid at one Well is released. A

movement of fluid through the channel from the well under pressure to the other well occurs, thereby scouring out the path established.

A still further means of establishing communication through the combustible seam between the wells may be adopted. For example, a machine gun may be mounted on the umbrella type of whipstock and explosive bullets fired into the seam progressively penetrating further into the seam. The channel thus established may be flushed and cleaned between successive shots.

Other means by which a direct path through the seam may be produced include so-called directional shooting, and the use of an oxygen lance connected to the end of a flexible hose. All the above methods may be used singly or in combination.

The present invention is more fully described and illustrated by reference to the accompanying drawings, the figures of which illustrate the various alternative embodiments of the present invention and are not intended to constitute a limitation thereof in which:

Figure 1 is a diagrammatic representation in plan of an oil field interstratified with coal to which the method of the present invention is applicable;

Fig. 2 is a diagrammatic view, partly in section taken on line 22 of'Fig. 1, of that embodiment of the invention in which there is no communication between the oil sands and the coal seam; and

Fig. 3 is a diagrammatic representation, partly in section, of that embodiment of the invention in which the oil sands communicate with the coal seam.

Referring to Fig. 1, a well I communicates with a seam of coal, through which a horizontal bore 3 is established. A chimney well 4 is drilled into the coal seam from the surface near the closed end of bore 3," thereby establishing a con.- tinuous passage fora combustionsupporting gas in' order to :burn the' coal-seam. .Oil wells 30 and 40 are drilled into. the oil-containing sands adjacent to'the coal seam. Upon combustion of the coal, a zone of heatingis created which volatilizes and fluidizes the oil in the sands within the zone of heating. The oil is recovered by introducing air or a gastun'der pressure intothe heated oil sandsthroughwell 3001*.40 and pumpingtheother-well. Referring now toFig, 3. a coalseam A is shown located below an oil containing. sand B, with an intervening layer of rock or shale .C.'. .This rep-v resenrs conditions which-often occur in. certain geological formations where oil is found,,par,- ticularly in strata of Pennsylvanian and .Mississippian age. -A well I isdrilled to establish communicationfrom thesurfacetwith the located coa1i,seamA 1 H. At the bottom-of well lashot-hole 2 is formed by means of explosive charges, thereby enlargingthe diameter of the'wellbottom. An umbrella type of .whipstock is lowered into the shothole and spread into position. A fiexible' cable carrying a rotating bit is op'erated from the whipstock to effect horizontabdrilling.through the coal seam-.- 'After a horizontal boreo3 ofthe desired length has been drilled, the endof the bore is located with respect-to the surface according to the methods described; Communication with the end of the boreis then established by drilling well 4.- Explosive charges are then set off at'thebottom of well 4 and at the end of the bore 3 effecting a communication between the two shot-holes 2' and 5 and the.wells l and 4...

After removal of the drilling apparatus, well l is capped, and pipe line 6 is inserted into the well. This line carries "a packer 1 which is-placed just above the coal seam'.- -'-A cement plug 8 is then placed above the packernearly up to the oil sand. Pipe line 6 establishes adirect communication between coal seam A- and a source of compressed-air fed through-valve 9 and line Ill; The chimneywell 4= is-al'so provided with a casinghead ll and-with -an. exit line for the gaseous--products "of combustion of the. coal. Line 12 is provided with a valve [3 for controlling the fiow of the' gaseous productsof combustion. The cap of well -4 carr-ies apipe [4 extending nearlyto the bottom of well-4. A burner l5 maybe attached at the lower end of pipe 14. Pipe l4 may carryair alone supplied. from'line l 6 or a combustible mixture Of'{ air and gas. Supplied from lines 16 and-.IL. Welll is .provide with a pump l8 extending-to ,the'level of the oil sand. The casinghead [9 of; well I is, provided with an outlet 20 throughwhich gases issuing from thejwell canbe taken-to a stripping plant, and then to a boiler. by means of which the necessary power to operatefblowers and compressors can be generated. The gaseous products of combustion by passage through the oil sands are enriched ,in combustible I vapors; "so' that the stripped'gase's' constitutean excellent fuel. v The coal seamm'ay'jbe initially ignited in any suitable manner, as by electrical means-or by' a squib or incendiary shell dropped-down pipe line 6. To ensure ignition a'cylinder of oxygen may "-be' discharged into pipe line '6." Air i under I pressure is then continuously supplied to the coal seam through line a 6; Valve. 3 providing an exit for the products of combustiqnfrom :chimn'ey well 4:isinitiallydeft01 8 untiligniti ofxthercoal near "shot-hole tandalon the bore is actively. under way. After a suitable period, valve 13 is closed and the pressure of the air enteringpipe 6 is raised. The products of combustion of the coal are therefore forced to traverse the oil sand B back toward well I. Heat from the burning coal seam A enters the oil sand increasing the vapor pressure, and lowering the viscosity of the oil. The hot gaseous products of combustion enter the sand and tend to move the thinner fluids toward the region of lower pressure above the cement plug 8 in well I. The products of combustion leave the casinghead at 20 much enriched by the volatile portions of the oil. The displaced liquefied oil is removed from shothole 2 by pump I8.

The gaseous products of combustion containing the volatile distilled oil fractions are sent to a suitable stripping unit not shown in the drawings. The stripped gases may be utilized as repressuring gas for adjacent oil sands not communicating with the burning coal seam and, therefore, not traversed by the combustion gases.

, Although not shown in Fig. 3, the oil may be driven to an existin or drilled well communicating with the oil sands, which functions as a producing well in place of well I, such as well 30 or 40 as shown in Fig. 1. In such a modification the casing 2| of well I seals off communication of well I with the oil sands, replacing the cylindrical screen 22. The above-described procedure may be somewhat modified where due to the incomplete combustion of the coal, appreciable amounts of condensable tarry vapors are formed, and pass into the oil-containing sands with the gaseous products of combustion, thereby tending to clog the pores of the sands. With reference to Fig. 3, in this modification compressed air is fed through line It to pipe line l4 inserted through the easinghead ll of chimney well 4. The air thus injected into chimney well 4 mixes with the heated gaseous products of combustion in the. slot-hole 5 and effects further oxidation of the incompletely oxidized constituents thereof. As a result, clean hot gases containing a minimum of condensable tarry vapors are forced under pressure into the oil-containing ands.

A further modification consists of attaching a suitable gas burner I5 to pipe line I4 in the chimney well 4 prior to capping this well. A gas line H is provided with valve 23 connected to pipe line l4 inserted through the casing of the chimney well 4, and constitutes means for supplying gas to the burner. Upon operation of the gas burner, complete oxidation of any condensable tarry vapors is effected prior to passage of the gaseous products of combustion into the oil-containing sands B.

Referring now to Fig. 2, a preferred embodiment of the invention is shown wherein the gaseous products of combustion do not traverse the oil sands. In this embodiment no communication exists between the input well I, bore 3 or chimney well 4 for the coal seam, and the oil sands B. Drilled wells 30 and 40 communicating only with the oil sands are utilized for the recovery of the oil.

Air or gas under pressure is introduced into the casinghead 3| of well 30 through line 4|, valve 42, line 32 and valve 33, valve 43 being closed. The heated oil in sands B i driven into the well bottom 34 of well 40, and is recovered by pump. I8.; The air or gas containing the volatile oil fractions isvented from casinghead 35 of well Ml throughline 36 -which leads to a: strippi plant. The gaseous products of combustion are vented from chimney well 4 through valve [3, lines l2 and, valve 45 and line46, valve 41 being closed. This producer gas may be used as fuel for boilers or for driving prime movers to supply the mechanical energy for operating compressors, and the like.

These hot gases after removal of tar vapors may" alternatively be recirculated through the oil sands byintroduction under pressure into well 30 thereby imparting their sensible heat tothe oil sands;

An alternative procedure consists of using air or-some-other gas as the repressuring agent and heating the same by passage through line 48, heatexchanger 49, line 50, valve 43 and the input line 32' (Fig.2) for well 30. Gaseous products of combustion vented from chimney well 4: pass through valve 13, line [2, valve 41, heat exchanger 49 and exit through line 5!. It will be observed that in the process described, the pressuring gas passes in heat exchange relationship with the gaseous products of combustion'vented from the chimney well. Valves 42 and 45 are closed when this alternative procedure is practiced.

Themethod' of the present invention advantageously. utilizes substantially all of the available heat energy contained in the combustible organic matter to provide a thermal drive for efiecting the recovery of oil from oil-containing sands. In addition, no source of heat extraneous to the geological formation under treatment is required.

The method of the present invention effects a recovery of substantially all of the oil contained in the sands except for undistillable residues, and substantially avoids any destruction of the oil by direct combustion thereof.

The invention also provides the novel means of establishing communication through the seam of coal, or the,like by hydraulic lifting.

, Having thusdescribed our invention, we claim:

1. A method for the recovery of oil from oilcontaining deposits located in geological formations interstratified with other combustible organic matter, which comprises supplying av combustion supporting gas to the organic matter, initiating and maintaining combustion of said organic matter thereby heating by conduction the adjacent oil, passingv the'hot gaseou products of combustion under pressure through the oil-containing deposits to further heat the oil thereby vaporizing and fluidizing the'same, moving the oil toward a zone of lower pressure under pressure exerted by the'gaseous products of combustion, and withdrawing the thus vaporized and fluidized oil from said zone of lower pressure.

2. A methodaccording to claim 1 in which the heated gaseous products of combustion containing condensable oxidizable constituents are, contacted with additional combustion supporting gas prior to passage through theoil-containing de: posit.

3. A methodaccording to claim 1 in which the heated gaseous products of combustion containing condensable oxidized constituents are subjected to further combustion prior to passage through the oil-containing deposit.

4. A method for the recovery of oil from oilcontaining deposits located in geological formations interstratified with other combustible organic matter which comprises supplying a combustion supporting gas to the organic matter, initiating and maintaining combustion of said organicimatter thereby heating by conduction the adjacent oilto vaporize andl'fluidize; the; same, passing'ta gasiunderi pressure: through the oilcontaining deposit" to! .forcel'the oiltoward a. zone of lower' pressure, and withdrawingthe thus vaporized". and fluidized: oilv from the region of lower pressure.

5. A methodfor the. secondary recovery-of oil from oil-containingdeposits located in geological formations interstfatified with othercombustible organic matter which comprises supplying a combustionx'supporting gas to, the organic matter, initiating. and: maintaining combustion of said organic matter thereby. heating; by conduction the adjacent oil, ..venting. the hot gaseous prod-.- ucts; of-combustion to the surface,- passing a gas under pressure in heat exchange relation to the hot vented gaseous products of' combustion into the oil-containing deposit to further heat the oil thereby vaporizing and fiuidizing the same, forcing the'oil through the oil-containing deposit by'pressure of the gas toward a zone of lower pressure, and "withdrawing, the thus vaporized and fluidized oil-from the zone of lower pressure.

6. Aumethod for' producing oilirom partially depleted oil-containing-sands located in geological formations-interstratified with seams of other combustibleorganic matter which comprises drilling an .input: and a chimneywell into the seam at selected'positions alongv the length thereof said chimney. well being in" communication with the oil-containinggsands, establishing a channel throughsaidseam between said wells, passing a combustion, supporting gas under pressure through saidiinput well and channel, initiatirg and maintainingcombustion of the organic matter in the' seam thereby heatingthe adjacent oil-containingtsands by: conduction, closing said chimney-well after initiation oicombustion, forcing the heated gaseous-products of combustion from thechimneywellv through the oil-containing sands thereby; further heating thev oil to volatilize andi-fluidize-the same, moving the thus volatilized and fluidized zoil toia producing well by pressure of- 'the gaseousproducts of combustion, and recovering theoil from the producing well;

'7. A methodvitor producing oil from partially depleted oilecontaining :sands, located in geologicaliormationsinterstratified withseam of other combustible-organic, matter which comprises drillinganlnputeIa-ndm chimney well into the seam at. selected -positionsralongi the length thereof, establishing a' channel through said seam between said wells; passing a combustion supportinggas through said inputzwell and channel, initiating and maintaining combustion of the organic matter" in the-seam thereby heating the adjacent oil co'ntaining' sands by conduction, venting the; gaseous productsof combustion through said'chimneywell tothe surface, passing a gasunder pressureinto theoil-containing sands through another well communicating therewith to. force the thus heatedoil into a producingwell, ,and -withdmwt lgcthe oil from the producingwell.

3; A m od, accordingt claim 7 in which the gas passed into. the oil-containing sands is maintained in heat exchangelrelation to the hot gaseous: products oflcombustion vented from the chimney well;

9'. Amethodaccording to claim 7 in which the gas passed into the oilcontaining sands. com- 13 prises the vented gaseous products of combusion. 1 i 10. A methodfor producing oil from partially depleted oil-containing sands located in geological formations interstratified with seams of other combustible organic matter which comprises drilling an input and a chimney well into the seam at selected positions along the length thereof, said chimney well being in communication with the oil sands, establishing a channel through said seam between said wells, passing a combustion supporting gas through said input well and channel, initiating and maintaining combustion of the organic matter in the seam thereby heating the adjacent oil-containing sands by conduction, closing said chimney well after initiation of combustion, contacting the heated gaseous products of combustion containing condensable oxidizable constituents with additional combus- A bustion from the chimney well through the oilcontaining sands thereby further heating the oil to volatilize and fluidize the same, moving the thus vaporized and fluidized oil from the sands to the input well by pressure of the gaseous products of combustion, and withdrawing the oil from the input well.

11. A method according to claim 10 in which a gas burner is operated at the chimney well bottom in the presence of a combustion supporting gas to remove the condensables by oxidizing the same prior to passage of the products of combustion through the oil-containing sands.

12. A method for the production of an enriched combustible gas from oil-containing deposit located in geological formations interstratified with other combustible organic matter. which comprises supplying a combustion supporting gas to the organic matter, initiating and maintaining combustion of said organic matter thereby heating by conduction the adjacent oil,

' passing the hot gaseous products of combustion under pressure through the oil-containing deposits to further heat the oil thereby vaporizing and fluidizing the same, moving the oil toward a zone of lower pressure under pressure exerted by the gaseous products of combustion, and separately withdrawing the gaseous products of combustion enriched in combustible vapors by passage through the oil-containing deposit.

13. A method for the recovery of oil from geological formations in which oil and other comhustihie organic material are present in different strata which comprises igniting said other organic material to provide heat requisite to reduce the viscosity of said oil and withdrawing the said oil from the said formation.

14. The method of claim 13, in which said other organic material is coal.

15. The method of claim 13 in which said other organic material is lignite.

16. A method of producing oil from geological formations in which oil and other combustible organic material are present in different strata which comprises interconnecting an input well and a chimney well which penetrate the stratum containing said other combustible organic material by means of a channel passing through said stratum, said chimney well also being in communication with an oil bearing stratum, initiating combustion of said other organic material in said channel to provide heat to and reduce the viscosity of said oil, passing a combustion supporting gas under pressure through said input well and into said channel to maintain said combustion, and withdrawing said oil from the geological formation, at least a portion of the products of said combustion being vented through said chimney well.

EDMUND S. MERRIAML FREDERICK SQUIRES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 895,612 Baker Aug. 11, 1908 947,608 Betts Jan. 25, 1910 1,263,618 Squires Apr. 23, 1918 1,473,348 Howard Nov. 6, 1923 1,913,395 Karrick June 13, 1933 2,172,683 Reed Sept. 12, 1939 2,188,737 Hixon Jan. 30, 1940 2,204,018 Kingsley June 11, 1940 2,357,703 Teichmann Sept. 5, 194.4

2,365,591 Ranney Dec. 19, 1944 2,382,471 Frey Aug. 14, 1945 2,390,770 Barton et al. Dec. 11, 1945 2,444,755 Stefl'en July 6, 1948 

13. A METHOD FOR THE RECOVERY OF OIL FROM GEOLOGICAL FORMATIONS IN WHICH OIL AND OTHER COMBUSTIBLE ORGANIC MATERIAL ARE PRESENT IN DIFFERENT STRATA WHICH COMPRISES IGNITING SAID OTHER OR- 